We plan to use the electron microscope as a tool in several investigations of the eye. First it is our intention to reveal the fine structural pathology of several tumors of the eye. A second phase of our study involves the functional and morphological relationship of the pigment epithelium and neural retina in the developing eye of amphibians. Not only will their fine structure be studied but this will be associated with functional maturation of the retina by determining the electroretinogram (ERG). Finally a major effort will be made to study the differentiation of the porosity of intraocular blood vessels to various marker substances.